Effects of acid modification on physical properties of konjac glucomannan (KGM) films

Edible films prepared from partially acid-hydrolyzed konjac glucomannan (KGM) were characterised with respect to the influence of altered chain length and molecular weight distribution on water sorptive capacity (WSC), water vapour permeability (WVP), thermal, and tensile properties. Acid treatment produced films with higher WSC and WVP, and lower melting enthalpy than that of an untreated one. These effects were attributed to an increase in the number of shorter chains, which contributed to more active sites for moisture sorption but disfavoured the formation of junction zones. The elastic modulus (EM) and tensile strength (TS) increased initially with decreasing molecular weight and increasing polydispersity, and then decreased with further reduction in molecular weight. Conversely, tensile elongation (TE) exhibited the opposite trend.